The use of tapping machines for tapping openings in pipelines is well-known. Prior issued U.S. Pat. No. 3,614,252 entitled TAPPING APPARATUS; U.S. Pat. No. 4,579,484 entitled UNDER WATER TAPPING MACHINE; U.S. Pat. No. 4,880,028 entitled COMPLETION MACHINES; U.S. Pat. No. 5,439,331 entitled HIGH PRESSURE TAPPING APPARATUS; and U.S. Pat. No. 6,012,878 entitled PRESSURE SUBSEA TAPPING MACHINES are examples of prior issued patents relating to tapping machines. These patents are incorporated herein by reference since they provide a thorough background relating to the subject matter of the present invention.
The typical tapping machine is formed of a body which is elongated and tubular. The body has a rotating boring bar therein. The lower end of the body is provided with means, such as a flange, by which it is secured to a fitting attached to a pipeline. A gear box is affixed to the upper end of the tapping machine body and provides means for rotation of the boring bar. The lower end of the boring bar is equipped to receive a cutter. Rotative energy, such as provided by a hydraulic motor, is supplied to the gear box and this rotative force in turn is applied to rotate the boring bar.
In addition to the boring bar, the tapping machine has a feed screw for moving the boring bar axially when the boring bar is rotated relative to the feed screw. Typically, a drive sleeve rotates the boring bar to provide such relative rotation and to rotate the cutter attached to the boring bar to cause the cutter to cut a hole in a pipe. The boring bar may have either a fixed or variable feed rate depending upon the design of the tapping machine.
The tapping machine to which the present invention is particularly adaptable is basically of the previously known structures as summarized above. However, the invention herein solves a serious problem that has interfered with completely satisfactory applications of known tapping machines for tapping into a vessel, such as a pipe, having therein high temperature fluids, either liquids or gases.
The essence of the invention herein is the provision of a unique bearing design incorporated in a tapping machine to rotatably support the boring bar at the tapping machine lower end in a way that compensates for sudden temperature changes as are encountered when a boring bar drill penetrates into a vessel having high temperature liquids or gases therein. Specifically, the invention herein provides a tapping machine having as an integral part thereof, a temperature compensating bearing—that is, the bearing as employed in a high temperature tapping machine of this invention provides for temperature compensation. The unique bearing accepts thermal expansion of a boring bar whereby the bearing continually rotatably supports a boring bar under substantial temperature changes without seizing or binding upon the surface of the boring bar.
For additional background information relating to bearings, including temperature compensating bearings, reference may be had to the following previously issued United States patents:
PUBLICATIONPATENT NO.NO.INVENTORTITLE03020113 AKiyoshiThermal Expansion Absorbing Bearing  527,877O'NeilApparatus For Tapping Mains2,515,383SnevaDrill Jig Bushing3,206,264Dalzell et al.High Temperature Bearings4,169,637VoitasDrill Bushings, Pump Seals and SimilarArticles4,848,935Seibig et al.Adapter Element5,380,112Schicktanz et al.Assembly For Concentrically Positioning ACasing Relative To A Shaft5,538,370GlennDevice For Drilling A Square Hole5,938,344SabinTemperature Compensating Bearing